Open source protobuf gmock matchers

[rohitsaboo]

Hey folks,

Is it possible to open source the protobuf gmock matchers?

Thanks,
Rohit

[davidzchen]

This has been opened since 2017, and there are many disparate fragments and variations of the proto gmock matchers floating around. It would be great to have an officially maintained version.

Are there any plans to do this?

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[davidzchen]

Has there been any progress on this?

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[tonyliaoss]

Hello,

The reason that this hasn't been done after all this time is due to a slightly-weird ownership model. Matchers like EqualsProto are not owned by GoogleTest. Internally EqualsProto uses MessageDifferencer that actually does the matching, and of course, we own MessageDifferencer.

I think the right way to think about this is that the core GoogleTest shouldn't need to know about protobufs. If anything, Protobuf should depend on GoogleTest, instead of the other way around.

Internally within Google though, GoogleTest folks are the ones supporting matchers like EqualsProto, while we support MessageDifferencer. This isn't a big deal if you have a monorepo like Google, but in the open source world every package has a different repo, "lockstep changes" can be harder to make.

Expanding a bit on what I mean by "lockstep changes": imagine there is a single change in GoogleTest that necessitated changes in something like EqualsProto. Now in order to export this change, two PRs needs to be sent simultaneously to both GoogleTest and Protobuf, and integration tests for each repo will fail, because they are still running with the old version of protobuf/googletest.

I think this is something we want to open source eventually, because Google is using/starting more and more third party projects -- and not being able have EqualsProto etc can be quite a pain. We just need to figure out the support story here first.

[tonyliaoss]

This seems related to google/googletest#1761